An extremely unpredictable event that produces potentially drastic effects on markets. Black swan events are characterized by their rarity, impact, and general belief “we should have seen it coming.” Examples of a black swan event are 9/11, the 2008 financial crisis, and the global COVID-19 response. Black swan trading is an entire trading philosophy based around the probability of a black swan event hitting the markets. Traders of this school are always buying options and never selling.
We don't know everything about the markets. We're just devoted to learners. Taken from those smarter than ourselves, here's how we define Black Swan.